Fire-extinguishing compositions must meet a whole complex of requirements:
The maintenance of all the requirements interferes with the problems concerning the reciprocal, often conflicting with one another, effects of the factors related to the technology of preparation of fire-extinguishing compositions and their characteristics. For example, the requirement of high fire-extinguishing efficiency makes it necessary to use a large amount of solid fillers (oxidizing agents, combustible agents) in the compositions. However, the increase of the portion of solid fillers leads to an increased molding pressure, which in turn increases the hazardness of the process and its energy capacity. The high molding pressure leads due to the increased surface friction between the particles of the solid fillers to the appearance of stress at the contact point of the particles, the formation of pores and, consequently, to a decrease of the stability and also to a non-uniform distribution of the particles in the molded composition, which leads to its non-uniform combustion and, as a consequence, to a decrease of the fire-extinguishing efficiency.
For the development of novel compositions and the improvement of known compositions, the problem is said to meet the sum of present requirements or to significantly improve separate properties and characteristics.
A composition for extinguishing fires is known (RU 2001647), which contains as combustible binder an epoxide resin in an amount of 10-14.5% by weight, an isomethyltetrahydrophthalic anhydride curing agent in an amount of 12-15% by weight, potassium perchlorate in an amount of 2-25% by weight as oxidizing agent, as additives carbon or a pigment in an amount of 0.001-0.5% by weight, sulforicinate in an amount of 0.01-0.5% by weight, and potassium nitrate the balance. When said composition is used, the fire-extinguishing concentration amounts to 23-27 g/m.sup.3.
A composition for extinguishing fires is known (RU 2001648), which contains an epoxide resin in an amount of 1.5-15% by weight as combustible binder, isomethyltetrahydrophthalic anhydride in an amount of 1.5-15% by weight as curing agent, and additionally a polyether (polyester) resin in an amount of 7.5-30% by weight, methylethylketone peroxide in an amount of approximately 0.075% by weight, potassium perchlorate in an amount of 10-40% by weight as oxidizing agent, as additives sulforicinate or carbon in an amount of 0.001-0.5% by weight, and potassium nitrate the balance. The composition possesses an increased impact resistance if it contains the epoxy resin in an amount of 1.5% by weight and the polyether (polyester) resin in an amount of not more than 30% by weight. There exists also a lower content limit for the polyether (polyester) resin, i.e. 7.5% by weight, but in this case the epoxy resin must be present in an amount of up to 15% by weight.
The process for the preparation of the compositions for extinguishing fires according to RU 2001647 and RU 2001648 comprises the steps of successive charging and mixing of the components of the composition. Said process comprises:
Charging of the binder and the curing agent (epoxy resin and isomethyltetrahydrophthalic anhydride, and according to RU 2001648 additionally the polyether (polyester) resin and methylethylketone peroxide) and mixing within 30 minutes at a temperature of 20.degree. C. with evacuation.
Charging of two doses of alkali metal nitrate with mixing for 10 minutes.
Charging of two doses of alkali metal perchlorate with mixing for 10 minutes and subsequent mixing of the components for 1 hour.
Charging of carbon or sulforicinate and mixing of all components for 30 minutes, whereby the last 20 minutes are carried out with evacuation.
The final composition is poured into forms and cured for 7-10 days at 80.degree. C.
As a result, an article of predetermined shape is obtained, which may be used for extinguishing fires by means of its ignition by an initiating system.
Said compositions and the process for their preparation possess a series of essential disadvantages:
Pyrotechnical compositions for use in a process for extinguishing voluminous fires are known (EP 0561035 B1). The first composition contains potassium perchlorate in an amount of 40-50% by weight, epoxy resin in an amount of 9-12% by weight, potassium chloride in an amount of 10-44% by weight, and magnesium powder in an amount of up to 4% by weight. A second composition contains potassium nitrate in an amount of 70-80% by weight, epoxy resin in an amount of 19-23% by weight and magnesium or aluminium powder in an amount of 2-4% by weight.
Said pyrotechnical compositions possess several essential disadvantages:
A composition for extinguishing fire and a process for its preparation are known (WO 92/17244) which contains alkali metal nitrate and/or perchlorate in an amount of 55-90% by weight, a combustible binder in an amount of 10-45% by weight, such as iditol or a ballistic propellant. Additionally, the composition may contain a combustible binder in an amount of 1-42% by weight, for example, dicyandiamide, and also ammonium perchlorate in an amount of 5-32% by weight as additional oxidizing agent.
The process for preparing the composition is characterized in that the starting components (KNO.sub.3, iditol, dicyandiamide) are prepared by grinding large agglomerates of particles and subsequent mixing of the powdery substances in a predetermined proportion. The prepared mixture is subjected to a blind pressing step and afterwards may be used as fire-extinguishing agent.
Said composition and process for its preparation possess several essential disadvantages:
The pyrotechnical aerosol-forming composition for extinguishing fires and the process for its preparation as disclosed in RU 2101054 represents the closest prior art for the present invention. The composition contains as oxidizing agent potassium nitrate in an amount of 67-72% by weight, as combustible binder phenolformaldehyde resin in an amount of 8-12% by weight and as gas-aerosol-forming agent dicyandiamide representing the balance. The composition additionally may contain potassium bicarbonate or potassium benzoate or potassium hexacyanoferrate in an amount of 4-12% by weight.
The process for the preparation of said pyrotechnical compositions comprises the step of mixing potassium nitrate with a specific surface area of its particles of no less than 1,500 cm.sup.2 /g and the combustible binder being a phenolformaldehyde resin in admixture with ethanol and acetone in a ratio of 30-50:70-50. Afterwards, the solution is mixed with powdery potassium nitrate and the gas-aerosol-forming agent until a uniform distribution is achieved. Subsequently, the mixture is dried and granulated with simultaneously drying at a temperature of 20-70.degree. C. until a residual content of moisture and volatile constituents of not more than 1% is present. The composition prepared according to such a process may be molded by means of blind pressing and used as a fire-extinguishing agent.
This composition and process for its preparation possess several essential disadvantages: